Core-First Synthesis of Three-, Four-, and Six-Armed Star-Shaped Poly(methyl methacrylate)s by Group Transfer Polymerization Using Phosphazene Base

The core-first synthesis of three-, four-, and six-armed star-shaped poly(methyl methacrylate)s (PMMAs) with predicted molecular weights and narrow molecular weight distributions ( M w / M n s) was carried out by the t -Bu-P 4 -catalyzed group transfer polymerization (GTP) of methyl methacrylate (MMA) using the newly designed silyl enolates, such as 1,1,1-tris[2-methyl-1-(trimethylsilyloxy)prop-1-enyloxymethyl]propane (EtC(MTS) 3 ), tetrakis{[2-methyl-1-(trimethylsilyloxy)prop-1-enyloxy]methyl}methane (C(MTS) 4 ), and bis{2,2,2-tris[2-methyl-1-(trimethylsilyloxy)prop-1-enyloxy]ethyl}ether (O(C(MTS) 3 ) 2 ), respectively. The absolute molecular weight ( M w (MALS)) of the obtained polymers proportionally increased with the increasing [MMA] 0 /[initiator] 0 ratio, and the highest molecular weight was ca. 132 kg mol –1 . Characterizations for the star-shaped PMMAs were conducted by cleavage and intrinsic viscosity [η] experiments. Cleavage experiments of the star-shaped PMMAs provided the evidence for homogeneous growth of the each arm in the t -Bu-P 4 -catalyzed GTP. The number of arm determined from the shrinking factors ( g ′) of [η] also supported the successful syntheses of the star-shaped polymers by the present core-first method. The versatility of this core-first method toward other methacrylic monomers was confirmed by the t -Bu-P 4 -catalyzed GTPs of allyl methacrylate (AMA), stearyl methacrylate (SMA), and 2-(dimethylamino)ethyl methacrylate (DMAEMA) using C(MTS) 4 as an initiator leading to well-defined star-shaped polymers.